Extendable ladders are ladders, which may be extended for use and folded for storage when not used. In the European patent EP-B1-0 527 766 a collapsible ladder is described comprising ladder bars divided into sections interconnected by rungs. In each ladder section is provided retaining or locking mechanisms, designed to automatically release the upper ladder sections, when a rung reaches a lower rung. This means, that subsequent to the release of the lowermost ladder section, the following ladder sections are automatically released, whereby the ladder collapses. However, when collapsing the ladder, the rungs are collapsing on top of each other, thereby generating a safety problem for the user's hands and fingers.
Thus, there is a need for a collapsible ladder, which allows the ladder sections to be automatically released by release of the lowermost ladder section, but which provides a safety distance between the rungs to avoid injuries of a users hands or fingers.
U.S. Pat. No. 7,048,094 also discloses an extendable ladder, which ladder comprises: a first stile, a second stile and a plurality of rungs disposed between the first stile and the second stile, the first stile being composed of a first column assembly including a first column and a second column assembly including a second column, the first column having an internal surface, and the second column being connected with the first column in a nested arrangement to form a telescopic mechanism capable of movement lengthwise; a locking mechanism for selectively locking the second column with respect to the first column; a button operably connected to the locking mechanism for controlling the locking mechanism; a ring is coupled to the first column proximate a distal end thereof, and the second column includes a sleeve coupled to the second column proximate a proximal end thereof. The sleeve includes an external guiding surface for contacting the internal surface of the first column and the ring includes an internal guiding surface for contacting an exterior surface of the second column. The columns are made of Aluminium while the ring and the sleeve are made of a plastic material.
However, the sleeve is made of a relatively thin plastic material and may be worn out during use, whereby its function for providing a guiding surface is reduced. Thus, there is a need for a collapsible ladder, for which a first collapsible column is provided with a guiding part for guiding the first column into a next lower, second column, and for which the guiding part is not easily worn out.